#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define FORI(i, n) for(ll i = 0; i < n; i++)
#define FOR(i, n) for(ll i = 1; i <= n; i++)
typedef vector<ll> vl;
typedef set<ll> setl;
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define pll pair<ll, ll>
#define db double
#define nll cout << "\n"
#define nl "\n"
#define sync ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
struct DSU{
vl par;
int components;
DSU(int sz = 1){
components = sz;
par.resize(sz + 5, -1);
}
int Find(int u){
if(par[u] < 0) return u;
else return par[u] = Find(par[u]);
}
bool Union(int u, int v){
u = Find(u), v = Find(v);
if(u != v){
if(par[u] < par[v]){
swap(u, v);
}
par[u] += par[v];
par[v] = u;
components--;
return true;
}
else{
return false;
}
}
};
const ll MOD = 1e9 + 7;
const int MAX = 2e5 + 5;
ll n, m, k, res;ll a[MAX];
vector < ll > g[MAX];
ll dp[MAX];
ll used[MAX];
void dfs(ll v){
used[v] = 1;
dp[v] = a[v];
vl cur;
for(auto i : g[v]){
if(!used[i]){
dfs(i);
dp[v] += dp[i];
cur.push_back(dp[i]);
}
}
sort(all(cur));
while(dp[v] > k){
res++;
dp[v] -= cur.back();
cur.pop_back();
}
}
void solve(){
cin >> n >> k;
FOR(i, n)cin >> a[i];
ll u, v;
FOR(i, n - 1){
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1);
cout << res;
}
signed main(){
// freopen("input.txt","r",stdin);
// freopen("output.txt","w",stdout);
sync;
ll t = 1;
// cin >> t;
FOR(i, t){
// cout << "Case #" << i << ": ";
solve();
}
}
